Zoom lens system for use in copying apparatus

ABSTRACT

A zoom lens system, for use in a copying apparatus, is provided with, from the object side, a first lens unit of a negative power including a negative lens element, a second lens unit of a positive power including a positive lens element and a negative meniscus lens element concave to the image side, an aperture stop, a third lens unit arranged symmetrically with the second lens unit with respect to the aperture stop, and a fourth lens unit arranged symmetrically with the first lens unit with respect to the aperture stop. The second lens unit and the fourth lens unit are moved in a same direction in association with each other so that the total length of the zoom lens system is minimum at unity magnification. The aperture stop moves so that the symmetry of the entire zoom lens system is maintained. An object-image distance is maintained constant by moving the entire zoom lens system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens system, and moreparticularly, to a zoom lens system, for use in a copying apparatus,where zooming is performed with a constant conjugate distance.

2. Description of the Prior Art

In a conventionally-used copying apparatus, in order to vary themagnification, the conjugate distance is varied by moving a mirror as aprojecting lens moves. For such a copying apparatus, since the mirror ismoved in order to vary the conjugate distance, a mechanism for movingthe mirror is required. For this reason, the copying apparatus isdisadvantageous in reducing size and cost.

In resent years, zoom lens systems have been proposed which are used forvarying the magnification in a copying apparatus.

For example, Japanese laid-open Patent Application No. S59-67512discloses an orthometa-type zoom lens system for use in a copyingapparatus which lens system is arranged symmetrically with respect to anaperture stop and includes six lens elements grouped into four units. Inthe lens system, the most object side lens element and the most imageside lens element are negative lenses. The half view angle thereof is14° to 18°.

U.S. Pat. No. 4,813,773 discloses a zoom lens system for use in acopying apparatus which lens system is arranged symmetrically withrespect to an aperture stop and includes four lens elements grouped intofour units. In the lens system, the most object side lens element andthe most image side lens element are negative lenses. The half viewangle thereof is 17° to 21°.

SUMMARY OF THE INVENTION

A principal object of the present invention is to provide a zoom lenssystem where aberrations are excellently corrected in a larger zoomrange compared to conventional zoom lens systems.

Another object of the present invention is to provide a zoom lens systemwhere aberrations are excellently corrected at a wider angle of viewcompared to conventional zoom lens systems.

Still another object of the present invention is to provide a compacterzoom lens system.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of this invention will become clearfrom the following description taken in conjunction with the preferredembodiments with reference to the accompanied drawings in which:

FIG. 1 is a cross-sectional view of the lens arrangement of a zoom lenssystem according to a first implementation of the present invention;

FIG. 2 is a diagram showing movements of lens units from a magnificationlarger than unity to a magnification smaller than unity;

FIG. 3 is a cross-sectional view of the lens arrangement of a firstembodiment of the present invention;

FIGS. 4A and 4B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the first embodimentat unity magnification;

FIGS. 5A and 5B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the first embodimentat a magnification larger than unity;

FIGS. 6A and 6B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the first embodimentat a magnification smaller than unity;

FIG. 7 is a cross-sectional view of the lens arrangement of a secondembodiment of the present invention;

FIGS. 8A and 8B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the second embodimentat unity magnification;

FIGS. 9A and 9B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the second embodimentat a magnification larger than unity;

FIGS. 10A and 10B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the second embodimentat a magnification smaller than unity;

FIG. 11 is a cross-sectional view of the lens arrangement of a thirdembodiment of the present invention;

FIGS. 12A and 12B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the third embodimentat unity magnification;

FIGS. 13A and 13B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the third embodimentat a magnification larger than unity;

FIGS. 14A and 14B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the third embodimentat a magnification smaller than unity;

FIG. 15 is a cross-sectional view of the lens arrangement of a fourthembodiment of the present invention;

FIGS. 16A and 16B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fourth embodimentat unity magnification;

FIGS. 17A and 17B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fourth embodimentat a magnification larger than unity;

FIGS. 18A and 18B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fourth embodimentat a magnification smaller than unity;

FIG. 19 is a cross-sectional view of the lens arrangement of a fifthembodiment of the present invention;

FIGS. 20A and 20B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fifth embodimentat unity magnification;

FIGS. 21A and 21B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fifth embodimentat a magnification larger than unity;

FIGS. 22A and 22B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fifth embodimentat a magnification smaller than unity;

FIG. 23 is a cross-sectional view of the lens arrangement of a zoom lenssystem according to a second implementation of the present invention;

FIG. 24 is a diagram showing movements of lens units from amagnification larger than unity to a magnification smaller than unity;

FIG. 25 is a cross-sectional view of the lens arrangement of a sixthembodiment of the present invention;

FIGS. 26A and 26B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the sixth embodimentat unity magnification;

FIGS. 27A and 27B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the sixth embodimentat a magnification larger than unity;

FIGS. 28A and 28B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the sixth embodimentat a magnification smaller than unity;

FIG. 29 is a cross-sectional view of the lens arrangement of a seventhembodiment of the present invention;

FIGS. 30A and 30B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the seventh embodimentat unity magnification;

FIGS. 31A and 31B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the seventh embodimentat a magnification larger than unity;

FIGS. 32A and 32B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the seventh embodimentat a magnification smaller than unity;

FIG. 33 is a cross-sectional view of the lens arrangement of an eighthembodiment of the present invention;

FIGS. 34A and 34B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eighth embodimentat unity magnification;

FIGS. 35A and 35B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eighth embodimentat a magnification larger than unity;

FIGS. 36A and 36B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eighth embodimentat a magnification smaller than unity;

FIG. 37 is a cross-sectional view of the lens arrangement of a ninthembodiment of the present invention;

FIGS. 38A and 38B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the ninth embodimentat unity magnification;

FIGS. 39A and 39B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the ninth embodimentat a magnification larger than unity;

FIGS. 40A and 40B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the ninth embodimentat a magnification smaller than unity;

FIG. 41 is a cross-sectional view of the lens arrangement of a tenthembodiment of the present invention;

FIGS. 42A and 42B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the tenth embodimentat unity magnification;

FIGS. 43A and 43B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the tenth embodimentat a magnification larger than unity;

FIGS. 44A and 44B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the tenth embodimentat a magnification smaller than unity;

FIG. 45 is a cross-sectional view of the lens arrangement of an eleventhembodiment of the present invention;

FIGS. 46A and 46B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eleventhembodiment at unity magnification;

FIGS. 47A and 47B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eleventhembodiment at a magnification larger than unity;

FIGS. 48A and 48B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eleventhembodiment at a magnification smaller than unity;

FIG. 49 is a cross-sectional view of the lens arrangement of a twelfthembodiment of the present invention;

FIGS. 50A and 50B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the twelfth embodimentat unity magnification;

FIGS. 51A and 51B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the twelfth embodimentat a magnification larger than unity;

FIGS. 52A and 52B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the twelfth embodimentat a magnification smaller than unity;

FIG. 53 is a cross-sectional view of the lens arrangement of athirteenth embodiment of the present invention;

FIGS. 54A and 54B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the thirteenthembodiment at unity magnification;

FIGS. 55A and 55B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the thirteenthembodiment at a magnification larger than unity;

FIGS. 56A and 56B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the thirteenthembodiment at a magnification smaller than unity;

FIG. 57 is a cross-sectional view of the lens arrangement of afourteenth embodiment of the present invention;

FIGS. 58A and 58B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fourteenthembodiment at unity magnification;

FIGS. 59A and 59B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fourteenthembodiment at a magnification larger than unity;

FIGS. 60A and 60B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fourteenthembodiment at a magnification smaller than unity;

FIG. 61 is a cross-sectional view of the lens arrangement of a fifteenthembodiment of the present invention;

FIGS. 62A and 62B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fifteenthembodiment at unity magnification;

FIGS. 63A and 63B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fifteenthembodiment at a magnification larger than unity;

FIGS. 64A and 64B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the fifteenthembodiment at a magnification smaller than unity;

FIG. 65 is a cross-sectional view of the lens arrangement of a sixteenthembodiment of the present invention;

FIGS. 66A and 66B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the sixteenthembodiment at unity magnification;

FIGS. 67A and 67B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the sixteenthembodiment at a magnification larger than unity;

FIGS. 68A and 68B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the sixteenthembodiment at a magnification smaller than unity;

FIG. 69 is a cross-sectional view of the lens arrangement of aseventeenth embodiment of the present invention;

FIGS. 70A and 70B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the seventeenthembodiment at unity magnification;

FIGS. 71A and 71B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the seventeenthembodiment at a magnification larger than unity;

FIGS. 72A and 72B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the seventeenthembodiment at a magnification smaller than unity;

FIG. 73 is a cross-sectional view of the lens arrangement of aneighteenth embodiment of the present invention;

FIGS. 74A and 74B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eighteenthembodiment at unity magnification;

FIGS. 75A and 75B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eighteenthembodiment at a magnifications larger than unity;

FIGS. 76A and 76B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the eighteenthembodiment at a magnification smaller than unity;

FIG. 77 is a cross-sectional view of the lens arrangement of anineteenth embodiment of the present invention;

FIGS. 78A and 78B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the nineteenthembodiment at unity magnification;

FIGS. 79A and 79B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the nineteenthembodiment at a magnification larger than unity;

FIGS. 80A and 80B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the nineteenthembodiment at a magnification smaller than unity;

FIG. 81 is a cross-sectional view of the lens arrangement of a twentiethembodiment of the present invention;

FIGS. 82A and 82B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the twentiethembodiment at unity magnification;

FIGS. 83A and 83B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the twentiethembodiment at a magnification larger than unity; and

FIGS. 84A and 84B are graphic representations of spherical aberration,astigmatism, distortion and lateral aberration of the twentiethembodiment at a magnification smaller than unity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will hereinafter be described withreference to the drawings.

As shown in FIG. 1, a first implementation of the present inventioncomprises from the object side: a first lens unit 1 including at leastone lens element and having a negative overall focal length; a secondlens unit 2 including a positive lens element and a negative meniscuslens element strongly concave to the aperture stop side and having apositive overall focal length; an aperture stop S; a third lens unit 3arranged symmetrically with the second lens unit 2 with respect to theaperture stop S; and a fourth lens unit 4 arranged symmetrically withthe first lens unit 1 with respect to the aperture stop S. In order toalways maintain constant an object-image distance from a magnificationlarger than unity to a magnification smaller than unity regardless ofmagnification as shown in FIG. 2, the power of the lens system isminimum at unity magnification. Moreover, in order to provide asymmetrical configuration to the lens system during zooming, the secondand the fourth lens units 2 and 4 are integrally moved by a same amountduring zooming so that the total length of the lens system increases,and the aperture stop S is also moved so as to be located in the middleof the second and the third lens units 2 and 3.

Such an arrangement is advantageous in correcting distortion,magnification chromatic aberration and coma can be corrected whilemaintaining the symmetry of the entire lens system regardless ofmagnification.

Moreover, at unity magnification, the power of the entire lens systemcan be made minimum and the total length of the lens system can be mademinimum by causing the distance between the first and the second lensunits 1 and 2 and the distance between the third and the fourth lensunits 3 and 4 to be minimum and by increasing the distance between thesecond and the third lens units 2 and 3.

According to the first implementation, a zoom lens system issymmetrically arranged, which is advantageous in performance as alimited distance zoom lens system including unity magnification.Moreover, in order to realize compactness, the zoom lens system isprovided with four lens units of negative, positive, positive andnegative configuration. Further, the zoom lens system can be arrangedwith six lens elements grouped into four units at a minimum, and sincethe second lens unit 2 of a positive power and the third lens unit 3 ofa positive power are of Gaussian type, the power of each lens can beincreased, so that a less lens movement amount is required duringzooming.

In a Gaussian-type lens system which is of symmetrical configuration, itis easy to correct spherical aberration and chromatic aberration, andcorrection performance of spherical aberration and chromatic aberrationbarely deteriorates even if the power of each lens is increased in orderto decrease the total length. This facilitates realization of a compactzoom lens system.

Moreover, with such an arrangement, a lens system is realized which hasa total length Σd/f of approximately 0.3 and is as compact as a normalfixed focus lens system.

Further, the most object side and the most image side negative lenselements cause an off-axial light beam to be incident on the succeedinglens elements at a shallow angle. Because of this, variation inaberration caused by an angle of view of the lens system is decreased.For this reason, the arrangement is suitable for a wide-angle lenssystem.

Subsequently, specific embodiments according to the first implementationwill be described with reference to the drawings.

FIG. 3 is a cross-sectional view of the lens arrangement of a firstembodiment of the present invention. The first embodiment comprises fromthe object side: a first lens unit 1 including a negative first lenselement; a second lens unit 2 including a positive second lens elementand a third lens element which is a negative meniscus lens elementstrongly concave to the aperture stop side and having a positive overallfocal length; an aperture stop S; a third lens unit 3 arrangedsymmetrically with the second lens unit 2 with respect to the aperturestop S; and a fourth lens unit 4 arranged symmetrically with the firstlens unit 1 with respect to the aperture stop S.

Table 1 shows data with respect to each surface of the first embodiment.In the table, r₁ to r₁₂ show radii of curvature, d₁ to d₁₂ show axialdistances, N₁ to N₆ and ν₁ to ν₆ show refractive indices and Abbenumbers, to the d-line, of each surface, respectively. Axial distancesd₂, d₆, d₇ and d₁₁ are variable during zooming. Values thereof at amagnification of -1.414, at unity magnification and a magnification of-0.640 are shown in Table 2.

FIGS. 4A and 4B to 6A and 6B show graphic representations of sphericalaberration, astigmatism, distortion and lateral aberration of the firstembodiment at unity magnification, at a magnification larger than unityand a magnification smaller than unity, respectively.

the first embodiment is a compact zoom lens system for use in a copyingapparatus which lens system includes six lens elements grouped into fourunits. Moreover, in the zoom lens system, aberrations are excellentlycorrected at each magnification at a wide angle of view, and a focallength can be reduced. Thereby, an optical system for use in a copyingapparatus can be reduced in size, and a large zoom ratio is available.

FIG. 7 and FIG. 11 show the lens arrangements of a second and a thirdembodiments of the present invention, respectively. The second and thethird lens embodiments comprise from the object side: a first lens unit1 including a negative first lens element; a second lens unit 2including a positive second lens element and a third lens element whichis a negative meniscus lens element strongly concave to the aperturestop side and having a positive overall focal length; an aperture stopS; a third lens unit 3 arranged symmetrically with the second lens unit2 with respect to the aperture stop S; and a fourth lens unit 4 arrangedsymmetrically with the first lens unit 1 with respect to the aperturestop S.

Moreover, the following conditions (1) to (4) are fulfilled:

    -1.3<f.sub.1 /f.sub.M <-0.7                                (1)

    0.5<f.sub.2 /f.sub.M <0.7                                  (2)

    0<r.sub.3 /r.sub.4,r.sub.10 /r.sub.9 <0.3                  (3)

    1.2<r.sub.3 /r.sub.5,r.sub.10 /r.sub.8 <1.8                (4)

where f_(M) is a focal length of the entire lens system at unitymagnification, f₁ is a focal length of the first lens unit 1, f₂ is afocal length of the second lens unit 2, and ri is a radius of curvatureof an ith surface counted from the object side.

Tables 3 and 5 show data with respect to each surface of the second andthe third embodiments, respectively. The axial distances d₂, d₆, d₇ andd₁₁ are variable during zooming. Values thereof at a magnification of-2.000, at unity magnification of -1,000 and at a magnification of-0.500 are shown in Tables 4 and 6.

The condition (1) relates to the power of the first lens unit 1 of anegative power and the power of the fourth lens unit 4 of a negativepower. By providing appropriate power to these lens units, aberrationscan excellently be corrected by associating these lens with the secondlens unit 2 of a positive power and the third lens unit 3 of a positivepower. When the upper limit of the condition (1) is exceeded, the powerof the second lens unit 2 and the power of the third lens unit 3increase, so that astigmatism is over-corrected. When the lower limit ofthe condition (1) is exceeded, astigmatism and distortion are notsufficiently corrected.

The condition (2) relates to the power of the second lens unit 2 and thepower of the third lens unit 3, and defines aberration correction andrealization of a compact zoom lens system. When the upper limit of thecondition (2) is exceeded, the power of the second lens unit 2 and thepower of the third lens unit 3 decrease. Although this is advantageousin correcting aberrations, a more lens movement amount is requiredduring zooming. Thereby, the total lens length increases at unitymagnification. On the other hand, when the lower limit of the condition(2) is exceeded, the power of the second lens unit 2 and the power ofthe third lens unit 3 increase, so that more aberrations are generatedand error sensitivity increases. As described above, a largemagnification range is not available in both cases.

The condition (3) defines the configurations of the second and the fifthlens elements and relates to aberration correction ability. That is,when the range of the condition (3) is exceeded, the diameter of thelens decreases, so that sufficient brightness cannot be secured.Moreover, the power of the second lens element and the power of thefifth lens element decrease, so that spherical aberration, distortionand coma cannot sufficiently be corrected.

The condition (4) defines a ratio of radius of curvature of a externallyconvex surface convex to the external side in the second and the thirdlens units 2 and 3, and relates to aberration correction ability. Whenthe upper limit of the condition (4) is exceeded, astigmatism and comacannot completely be corrected. Moreover, when the lower limit thereofis exceeded, coma is not sufficiently corrected.

FIGS. 8A and 8B to 10A and 10B, and FIGS. 12A and 12B to 14A and 14Bshow graphic representations of spherical aberration, astigmatism,distortion and lateral aberration of the second and the thirdembodiments, respectively, at unity magnification, at a magnificationlarger than unity and at a magnification smaller than unity.

Both the second and the third embodiments are compact zoom lens systemsfor use in a copying apparatus which lens systems include six lenselements grouped into four units. Moreover, in the zoom lens systems,aberrations are excellently corrected at a wide angle of view, and afocal length can be reduced. Thereby, an optical system in a copyingapparatus can be reduced in size, and it is possible to employ a largezoom ratio between -0.5× and -2.0× is available.

Subsequently, a fourth and a fifth embodiments of the present inventionwill be described.

The fourth and the fifth embodiments comprise from the object side: afirst lens unit 1 including a negative first lens element; a second lensunit 2 including a positive second lens element and a third lens whichis a negative meniscus lens element strongly concave to the aperturestop side and having a positive overall focal length; an aperture stopS; a third lens unit 3 arranged symmetrically with the second lens unit2 with respect to the aperture stop S; and a fourth lens unit 4 arrangedsymmetrically with the first lens unit 1 with respect to the aperturestop S.

Moreover, the following conditions (1)' to (4)' are fulfilled:

    -1.0<f.sub.1 /f.sub.M <-0.55                               (1)'

    0.4<f.sub.2 /f.sub.M <0.7                                  (2)'

    0<r.sub.3 /r.sub.4,r.sub.10 /r.sub.9 <0.3                  (3)'

    1.2<r.sub.3 /r.sub.5,r.sub.10 /r.sub.8 <1.8                (4)'

Description of the conditions (1)' to (4)' will be omitted, since it hasalready been given with respect to the conditions (1) to (4) of thefirst embodiment.

Tables 7 and 9 show data with respect to each surface of the fourth andthe fifth embodiments. The axial distances d₂, d₆, d₇ and d₁₁ arevariable during zooming. Values thereof at a magnification of -1.414×,at unity magnification of -1.000 and at a magnification of -0.640× areshown in Tables 8 and 10.

FIGS. 16A and 16B to 18A and 18B, and FIGS. 20A and 20B to 22A and 22Bshow graphic representations of spherical aberration, astigmatism,distortion and lateral aberration of the fourth and the fifthembodiments at unity magnification, at a magnification larger than unityand at a magnification smaller than unity, respectively.

Both fourth and fifth embodiments are compact zoom lens systems for usein a copying apparatus which lens systems include six lens elementsgrouped into four units. In the lens systems, aberrations areexcellently corrected at a wide angle of view of up to approximately 30°and a focal length can be reduced. Thereby, it is possible to reduce thesize of an optical system in a copying apparatus.

The second and the third embodiments are arranged so that a large zoomrange (between -0.5× and -2.0×) is obtained, and fulfill the conditions(1) to (4) in order to excellently correct aberrations in the large zoomrange. On the other hand, the fourth and the fifth embodiments arearranged so that a wide angle of view of nearly 30° is obtained, andfulfill the conditions (1)' to (4)' in order to excellently correctaberrations in the wide angle of view.

Subsequently, a second implementation of the present invention will bedescribed.

As shown in FIG. 23, the second implementation comprises from the objectside: a first lens unit 1 including at least one lens element and havinga negative overall focal length; a second lens unit 2 including apositive lens element and a negative meniscus lens element stronglyconcave to the aperture stop side and having a positive overall focallength; an aperture stop S; a third lens unit 3 arranged symmetricallywith the second lens unit 2 with respect to the aperture stop S; and afourth lens unit 4 arranged symmetrically with the first lens unit 1with respect to the aperture stop S. The four lens units aresymmetrically arranged, and moved as subsequently described.

In order to always maintain the object-image distance constantregardless of magnification as shown in FIG. 24, the power of the entirelens system is minimum at unity magnification. Moreover, during zooming,the second and the fourth lens units 2 and 4 are integrally moved by asame amount so that the total length of the lens system increases, andthe aperture stop S is relatively fixed with respect to the moving lensunits or the stationary lens units. Thereby, it is possible to group thelens elements of the lens system into two main blocks, so that the lensbarrel arrangement can largely be simplified. Moreover, the power of theentire lens system and the total length of the lens system can be mademinimum by arranging the lens system so that, at unity magnification,the distance between the first and the second lens units 1 and 2 and thedistance between the third and the fourth lens units 3 and 4 are minimumand that the distance between the second and the third lens units 2 and3 increases.

According to the second implementation, a zoom lens system issymmetrically arranged, which is advantageous in performance as alimited zoom lens system including unity magnification. Moreover, inorder to realize a compact zoom lens system, the zoom lens system isprovided with four lens units of negative, positive, positive andnegative configuration. Further, the zoom lens system can be arrangedwith six lens elements grouped into four lens units at a minimum, andsince the second lens unit 2 of a positive power and the third lens unit3 of a positive power are of Gaussian type, the power of each lens unitcan be increased, so that a less lens movement amount is required duringzooming. Moreover, in the lens system, since the lens system isasymmetrical in front and in rear of the aperture stop S during zooming,generation of coma can be restrained at a magnification larger thanunity. Further, with the above-described arrangement of the secondimplementation, a lens system is realized which has a total length Σd/fof approximately 0.3 and is as compact as a normal fixed focus lenssystem.

A zoom lens system according to the second implementation fulfills thefollowing conditions (1)", (2)", (5), (4)" and (6):

    -1.3<f.sub.1 /f.sub.M <-0.8                                (1)"

    0.5<f.sub.2 /f.sub.M <0.7                                  (2)"

    |r.sub.3 /r.sub.4 |,|r.sub.10 /r.sub.9 |<0.5                                            (5)

    1.2<r.sub.3 /r.sub.5,r.sub.10 /r.sub.8 <2.2                (4)"

    |n.sub.1 -n.sub.2 |<0.1                  (6)

where n₁ is a refractive index of a negative lens element of the firstlens unit 1 and n₂ is a refractive index of the positive lens element ofthe second lens unit 2.

Description of the conditions (1)", (2)" and (4)" will be omitted here,since it has already been given with respect to the conditions (1), (2)and (4) of the first implementation.

The condition (5) defines the configurations of the second and the fifthlens elements, and relates to aberration correction performance. Whenthe range defined by the condition (5) is exceeded, the diameter of thelens elements decrease, so that sufficient brightness cannot be secured.Moreover, the power of each lens element decreases, so that sphericalaberration, astigmatism and coma cannot sufficiently be corrected.

The condition (6) relates to the refractive indices of the first and thesecond lens units 1 and 2, and is a condition for limiting aberrationcorrection condition. When the range defined by the condition (6) isexceeded, generation of spherical aberration and astigmatism increases,so that it is impossible to completely correct them.

Subsequently, specific embodiments according to the secondimplementation will be described with reference to the drawings.

FIGS. 25 and 29 show the lens arrangements of a sixth and a seventhembodiments of the present invention. The sixth and the seventhembodiments comprise from the object side: a first lens unit 1 includingat least one lens element and having a negative overall focal length; asecond lens unit 2 including a positive lens element and a negativemeniscus lens element strongly concave to the aperture stop side andhaving a positive overall focal length; an aperture stop S; a third lensunit 3 arranged symmetrically with the second lens unit 2 with respectto the aperture stop S; and a fourth unit 4 arranged symmetrically withthe first lens unit 1 with respect to the aperture stop S. The sixth andthe seventh embodiments are zoom lens systems, for use in a copyingapparatus, where the second and the fourth lens units 2 and 4 are movedin a same direction in association with each other so that the totallens length is minimum at unity magnification and where zooming isperformed while the object-image distance is maintained constant. Atunity magnification, the lens units are symmetrical. That is, thedistance between the first and the second lens units 1 and 2 is equal tothe distance between the third and the fourth lens units 3 and 4, andthe distance between the second lens unit 2 and the aperture stop S isequal to the distance between the third lens unit 3 and the aperturestop S. Except at unity magnification, the distance between the secondlens unit 2 and the aperture stop S is not equal to the distance betweenthe third lens unit 3 and the aperture stop S. This means that the zoomlens system is asymmetrical at a magnification other than unitymagnification.

Tables 11 and 13 show data with respect to each surface of the sixth andthe seventh embodiments. The axial distances d₂, d₆, d₇ and d₁₁ arevariable during zooming. Values thereof at a magnification of -2.000×,at unity magnification and at a magnification of -0.500× are shown inTables 12 and 14.

FIGS. 26A and 26B to 28A and 28B and FIGS. 30A and 30B to 32A to 32Bshow graphic representations of spherical aberration, astigmatism,distortion and lateral aberration of the sixth and the seventhembodiments at unity magnification, at a magnification larger than unityand at a magnification smaller than unit, respectively.

The zoom lens systems for use in a copying apparatus are compact lenssystems of four-unit, six-element configuration. Moreover, in the lenssystems, aberrations are excellently corrected at each magnification ata wide angle of view, and the focal length can be reduced. Thereby, anoptical system for use in a copying apparatus can be reduced in size,and a large zoom ratio is available.

Subsequently, a third implementation of the present invention will bedescribed.

The third implementation is a zoom lens system, for use in a copyingapparatus, where magnification is varied by moving the entire lenssystem while the focal length is varied by moving a part of the lenssystem. A zoom lens system according to the third implementationcomprises from the object side: a first lens unit 1 including a negativelens element; a second lens unit 2 including a bi-convex lens elementand a negative meniscus lens element strongly concave to the aperturestop side; an aperture stop S; a third lens unit 3 arrangedsubstantially symmetrically with the second lens unit 2 with respect tothe aperture stop S; and a fourth lens unit 4 arranged substantiallysymmetrically with the first lens unit 1 with respect to the aperturestop S. During zooming, the second and the third lens units 2 and 3 aremoved substantially symmetrically with respect to the aperture stop S tovary the focal length. At this time, since the first and the fourth lensunits 1 and 4 are fixed with respect to the aperture stop S, the totallength of the lens system does not vary. Thereby, designing of a copyingapparatus is greatly facilitated. Moreover, since the focal length isvaried by moving the second and the third lens units 2 and 3 which havea strong power, the movement amounts of the second and the third lensunits 2 and 3 can be reduced. Thereby, a compact zoom lens system can berealized. Moreover, since the lens system is substantially symmetricalwith respect to the aperture stop S, high image forming performance isrealized at unity magnification, which is most important for a zoom lenssystem for use in a copying apparatus. Further, the zoom lens systemaccording to the third implementation has a wide angle of view (the halfview angle is 26°), and can cope with a half view angle of up toapproximately 30°.

A zoom lens systems according to the third implementation fulfills thefollowing condition (1)'", (2)" (7) and (8):

    -1.3<f.sub.1 /f.sub.M <-0.6                                (1)'"

    0.4<f.sub.2 /f.sub.M <0.7                                  (2)"

    -3.0<(1/r.sub.2 -1/r.sub.3)f.sub.M <-1.5                   (7)

    |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M |<0.02(8)

Description of the conditions (1)'" and (2)" will be omitted here, sinceit has already been given with respect to the conditions (1) and (2) ofthe first implementation.

The conditions (7) and (8) are conditions for limiting theconfigurations of the third lens element (of second lens unit 2) and thefourth lens element (of third lens unit 3) which are arranged close tothe aperture stop S. When the range defined by the condition (7) isexceeded, it is difficult to correct astigmatism. When the condition (8)is not fulfilled, it is difficult to correct coma.

Subsequently, specific embodiments according to the third implementationwill be described with reference to the drawings,

FIGS. 33, 37, 41, 45, 49, 53, 57, 61, 65, 69, 73, 77 and 81 show thelens arrangements of an eighth to a twentieth embodiments of the presentinvention, respectively. The eighth to twentieth embodiments comprisefrom the object side: a first lens unit 1 including a negative lenselement; a second lens unit 2 including a bi-convex lens element and anegative meniscus lens element strongly concave to the aperture stopside; an aperture stop S; a third lens unit 3 arranged substantiallysymmetrically with the second lens unit 2 with respect to the aperturestop S; and a fourth lens unit 4 arranged substantially symmetricallywith the first lens unit 1 with respect to the first lens unit 1. Duringzooming, the first and the fourth lens units 1 and 4 are fixed, and thesecond and the third lens units 2 and 3 are moved substantiallysymmetrically with respect to the aperture stop S.

Tables 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37 and 39 show datawith respect to each surface of the eighth to the twentieth embodiments,respectively. The axial distances d₂, d₆, d₇ and d₁₁ are variable duringzooming. Values thereof at a magnification of -1.414, at unitymagnification of -1.000 and at a magnification of -0.640 are shown inTables 16, 18, 20, 22, 24, 26, 28, 30, 32, 34 and 36. Values thereof ata magnification of -2.000, at unity magnification of -1.000 and at amagnification of -0.500 are shown in Tables 38 and 40.

FIGS. 34A and 34B to 36A and 36B, FIGS. 38A and 38B to 40A and 40B,FIGS. 42A and 42B to 44A and 44B, FIGS. 46A and 46B to 48A and 48B,FIGS. 50A and 50B to 52A and 52B, FIGS. 54A and 54B to 56A and 56B,FIGS. 58A and 58B to 60A and 60B, FIGS. 62A and 62B to 64A and 64B,FIGS. 66A and 66B to 68A and 68B, FIGS. 70A and 70B to 72A and 72B,FIGS. 74A and 74B to 76A and 76B, FIGS. 78A and 78B to 80A and 80B andFIGS. 82A and 82B to 84A and 84B show graphic representations ofspherical aberration, astigmatism, distortion and lateral aberration ofthe eighth to twentieth embodiments at unity magnification, at amagnification larger than unity and at a magnification smaller thanunity, respectively.

The zoom lens systems for use in a copying apparatus are compact lenssystems of four-unit, six-element configuration. Moreover, in the lenssystems, aberrations are excellently corrected at each magnification ata wide angle of view, and the focal length can be reduced. Thereby, anoptical system for use in a copying apparatus can be reduced in size,and a large zoom ratio is available.

                  TABLE 1                                                         ______________________________________                                        (Embodiment 1)                                                                f = 190.143 to 180.353                                                                         F.sub.NO = 8.0                                               f.sub.1 /f.sub.M = -1.173                                                                      f.sub.2 /f.sub.M = 0.648                                     r.sub.3 /r.sub.4 = r.sub.10 /r.sub.9 = 0.262                                                   r.sub.3 /r.sub.5 = r.sub.10 /r.sub.8 = 1.277                 Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -598.77                                                                                 d.sub.1 2.50   N.sub.1                                                                            1.6129                                                                              ν.sub.1                                                                         37.0                            r.sub.2                                                                            177.46                                                                                  d.sub.2 Variable                                               r.sub.3                                                                            40.74                                                                                   d.sub.3 6.00   N.sub.2                                                                            1.6779                                                                              ν.sub.2                                                                         53.4                            r.sub.4                                                                            155.61                                                                                  d.sub.4 1.89                                                   r.sub.5                                                                            31.92                                                                                   d.sub.5 4.80   N.sub.3                                                                            1.6545                                                                              ν.sub.3                                                                         33.9                            r.sub.6                                                                            23.65                                                                                   d.sub.6 Variable                                               S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            -23.65                                                                                  d.sub. 8                                                                              4.08   N.sub.4                                                                            1.6545                                                                              ν.sub.4                                                                         33.9                            r.sub.8                                                                            -31.92                                                                                  d.sub.9 1.89                                                   r.sub.9                                                                            -155.61                                                                                 d.sub.10                                                                              6.00   N5   1.6779                                                                              ν.sub.5                                                                         53.4                            r.sub.10                                                                           -40.74                                                                                  d.sub.11                                                                              Variable                                               r.sub.11                                                                           -177.46                                                                                 d.sub.12                                                                              2.50   N.sub.6                                                                            1.6129                                                                              ν.sub.6                                                                         37.0                            r.sub.12                                                                           598.77                                                                   ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        (Embodiment 1)                                                                ______________________________________                                        Magnification                                                                            -1.414       -1.000  -0.640                                        Focal length                                                                             184.16       109.14  189.35                                        Half view  18.6° 21.5°                                                                          18.0°                                  angle(ω)                                                                d.sub.2    2.420        0.570   3.642                                         d.sub.6    11.865       12.790  11.254                                        d.sub.7    11.865       12.790  11.254                                        d.sub.11   2.420        0.570   8.642                                         ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        (Embodiment 2)                                                                f = 190.375 to 167.913                                                                         F.sub.No. = 8.0                                              f.sub.1 /f.sub.M = -1.119                                                                      f.sub.2 /f.sub.M = 0.631                                     r.sub.3 /r.sub.4 = r.sub.10 /r.sub.9 = 0.252                                                   r.sub.3 /r.sub.5 = r.sub.10 /r.sub.8 = 1.301                 Radius of  Axial        Refractive Abbe                                       Curvature  Distance     Index      Number                                     ______________________________________                                        r.sub.1                                                                            -548.33                                                                                 d.sub.1 3.00   N.sub.1                                                                            1.6129                                                                              ν.sub.1                                                                         37.0                            r.sub.2                                                                            171.70                                                                                  d.sub.2 Variable                                               r.sub.3                                                                            40.98                                                                                   d.sub.3 6.00   N.sub.2                                                                            1.6779                                                                              ν.sub.2                                                                         53.4                            r.sub.4                                                                            162.91                                                                                  d.sub.4 1.89                                                   r.sub.5                                                                            31.49                                                                                   d.sub.5 4.08   N.sub.3                                                                            1.6545                                                                              ν.sub.3                                                                         33.9                            r.sub.6                                                                            23.50                                                                                   d.sub.6 Variable                                               S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            -23.50                                                                                  d.sub.8 4.08   N.sub.4                                                                            1.6545                                                                              ν.sub.4                                                                         33.9                            r.sub.8                                                                            -31.49                                                                                  d.sub.9 1.89                                                   r.sub.9                                                                            -162.91                                                                                 d.sub.10                                                                              6.00   N.sub.5                                                                            1.6779                                                                              ν.sub.5                                                                         53.4                            r.sub.10                                                                           -40.98                                                                                  d.sub.11                                                                              Variable                                               r.sub.11                                                                           -171.70                                                                                 d.sub.12                                                                              3.00   N.sub.6                                                                            1.6129                                                                              ν.sub.6                                                                         37.0                            r.sub.12                                                                           548.33                                                                   ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        (Embodiment 2)                                                                ______________________________________                                        Magnification                                                                            -2.000       -1.000  -0.500                                        Focal length                                                                             167.91       190.38  167.91                                        Half view  16.6° 21.5°                                                                          16.6°                                  angle (ω)                                                               d.sub.2    7.555        0.570   7.555                                         d.sub.6    9.297        12.790  9.297                                         d.sub.7    9.297        12.790  9.297                                         d.sub.11   7.555        0.570   7.555                                         ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        (Embodiment 8)                                                                f = 190.467 to 168.100                                                                         F.sub.NO = 8.0                                               f.sub.1 /f.sub.M = -1.014                                                                      f.sub.2 /F.sub.M = 0.594                                     r.sub.3 /r.sub.4 = r.sub.10 /r.sub.9 = 0.227                                                   r.sub.3 /r.sub.4 = r.sub.10 /r.sub.8 = 1.351                 Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -420.13                                                                                 d.sub.1 3.00   N.sub.1                                                                            1.6129                                                                              ν.sub.1                                                                        37.0                             r.sub.2                                                                            165.29                                                                                  d.sub.2 Variable                                               r.sub.3                                                                            41.23                                                                                   d.sub.3 6.00   N.sub.2                                                                            1.6779                                                                              ν.sub.2                                                                        53.4                             r.sub.4                                                                            181.25                                                                                  d.sub.4 1.89                                                   r.sub.5                                                                            30.51                                                                                   d.sub.5 4.80   N.sub.3                                                                            1.6545                                                                              ν.sub.3                                                                        33.9                             r.sub.5                                                                            23.05                                                                                   d.sub.6 Variable                                               S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            -23.05                                                                                  d.sub.8 4.08   N.sub.4                                                                            1.6545                                                                              ν.sub.4                                                                        33.9                             r.sub.8                                                                            -30.51                                                                                  d.sub.9 1.89                                                   r.sub.9                                                                            -181.25                                                                                 d.sub.10                                                                              6.00   N.sub.5                                                                            1.6779                                                                              ν.sub.5                                                                        53.4                             r.sub.10                                                                           -41.23                                                                                  d.sub.11                                                                              Variable                                               r.sub.11                                                                           -165.29                                                                                 d.sub.12                                                                              3.00   N.sub.6                                                                            1.6129                                                                              ν.sub.6                                                                        37.0                             r.sub.12                                                                           420.13                                                                   ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        (Embodiment 3)                                                                ______________________________________                                        Magnification                                                                            -2.000       -1.000  -0.500                                        Focal length                                                                             168.10       190.47  168.10                                        Half view  16.6° 21.5°                                                                          16.6°                                  angle(ω)                                                                d.sub.2    6.696        0.570   6.696                                         d.sub.6    9.727        12.790  9.727                                         d.sub.7    9.727        12.790  9.727                                         d.sub.11   6.696        0.570   6.696                                         ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                        (Embodiment 4)                                                                f = 200.048 to 189.888                                                                         F.sub.NO = 8.0                                               f.sub.1 /f.sub.M = -0.888                                                                      f.sub.2 /f.sub.M = 0.545                                     r.sub.3 /r.sub.4 = r.sub.10 /r.sub.9 = 0.090                                                   r.sub.3 /r.sub.5 = r.sub.10 /r.sub.8 = 1.540                 Radius of  Axial        Refractive Abbe                                       Curvature  Distance     Index      Number                                     ______________________________________                                        r.sub.1                                                                            -244.38                                                                                 d.sub.1 2.56   N.sub.1                                                                            1.6129                                                                              ν.sub.1                                                                         37.0                            r.sub.2                                                                            197.07                                                                                  d.sub.2 Variable                                               r.sub.3                                                                            51.53                                                                                   d.sub.3 7.17   N.sub.2                                                                            1.6779                                                                              ν.sub.2                                                                         53.4                            r.sub.4                                                                            572.49                                                                                  d.sub.4 2.54                                                   r.sub.5                                                                            33.47                                                                                   d.sub.5 5.16   N.sub.3                                                                            1.6545                                                                              ν.sub.3                                                                         33.9                            r.sub.5                                                                            25.89                                                                                   d.sub.6 Variable                                               S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            -25.89                                                                                  d.sub.8 5.16   N.sub.4                                                                            1.6545                                                                              ν.sub.4                                                                         33.9                            r.sub.8                                                                            -33.47                                                                                  d.sub.9 2.54                                                   r.sub.9                                                                            -572.49                                                                                 d.sub.10                                                                              7.17   N.sub.5                                                                            1.6779                                                                              ν.sub.5                                                                         53.4                            r.sub.10                                                                           -51.53                                                                                  d.sub.11                                                                              Variable                                               r.sub.11                                                                           -197.07                                                                                 d.sub.12                                                                              2.56   N.sub.6                                                                            1.6129                                                                              ν.sub.6                                                                         37.0                            r.sub.12                                                                           244.38                                                                   ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                        (Embodiment 4)                                                                ______________________________________                                        Magnification                                                                            -1.414       -1.000  -0.640                                        Foca1 length                                                                             193.84       200.05  189.89                                        Half view  24.2° 27.7°                                                                          23.3°                                  angle (ω)                                                               d.sub.2    1.914        0.584   2.796                                         d.sub.6    11.884       12.549  11.443                                        d.sub.7    11.884       12.549  11.443                                        .sub. d.sub.11                                                                           1.914        0.584   2.796                                         ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        (Embodiment 5)                                                                f = 195.167 to 185.289                                                                         F.sub.NO = 8.0                                               f.sub.1 /f.sub.M = -0.858                                                                      f.sub.2 /f.sub.M = 0.535                                     r.sub.3 /r.sub.4 = r.sub.10 /r.sub.9 = 0.100                                                   r.sub.3 /r.sub.5 = r.sub.10 /r.sub.8 = 1.582                 Radius of  Axial        Refractive Abbe                                       Curvature  Distance     Index      Number                                     ______________________________________                                        r.sub.1                                                                            -278.19                                                                                 d.sub.1 2.50   N.sub.1                                                                            1.6129                                                                              ν.sub.1                                                                         37.0                            r.sub.2                                                                            163.24                                                                                  d.sub.2 Variable                                               r.sub.3                                                                            50.01                                                                                   d.sub.3 7.00   N.sub.2                                                                            1.6779                                                                              ν.sub.2                                                                         53.4                            r.sub.4                                                                            501.25                                                                                  d.sub.4 1.57                                                   r.sub.5                                                                            31.60                                                                                   d.sub.5 5.04   N.sub.3                                                                            1.6545                                                                              ν.sub.3                                                                         33.9                            r.sub.6                                                                            24.83                                                                                   d.sub.6 Variable                                               S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            -24.83                                                                                  d.sub.8 5.04   N.sub.4                                                                            1.6545                                                                              ν.sub.4                                                                         33.9                            r.sub.8                                                                            -31.60                                                                                  d.sub.9 1.57                                                   r.sub.9                                                                            -501.25                                                                                 d.sub.10                                                                              7.00   N.sub.5                                                                            1.6779                                                                              ν.sub.5                                                                         53.4                            r.sub.10                                                                           -50.01                                                                                  d.sub.11                                                                              Variable                                               r.sub.11                                                                           -163.24                                                                                 d.sub.12                                                                              2.50   N.sub.6                                                                            1.6129                                                                              ν.sub.6                                                                         37.0                            r.sub.12                                                                           278.19                                                                   ______________________________________                                    

                  TABLE 10                                                        ______________________________________                                        (Embodiment 5)                                                                ______________________________________                                        Magnification                                                                            -1.414       -1.000  -0.640                                        Focal length                                                                             189.13       195.17  185.29                                        Half view  24.7° 28.3°                                                                          28.9°                                  angle (ω)                                                               d.sub.2    1.801        0.570   2.617                                         d.sub.6    11.829       12.444  11.421                                        d.sub.7    11.829       12.444  11.421                                        .sub. d.sub.11                                                                           1.801        0.570   2.617                                         ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                        (Embodiment 6)                                                                f = 190.467 to 168.100                                                                          F.sub.NO = 8.0                                              f.sub.1 /f.sub.M = -1.014                                                                       f.sub.2 /f.sub.M = 0.594                                    |r.sub.3 /r.sub.4 |, |r.sub.10 /r.sub.9            | = 0.227                                                                              r.sub.3 /r.sub.5 = r.sub.10 /r.sub.8 = 1.351                |n.sub.1 - n.sub.2 | = 0.065                                Radius of  Axial        Refractive Abbe                                       Curvature  Distance     Index      Number                                     ______________________________________                                        r.sub.1                                                                            -420.13                                                                                 d.sub.1 3.00   N.sub.1                                                                            1.6129                                                                              ν.sub.1                                                                         37.0                            r.sub.2                                                                            165.29                                                                                  d.sub.2 Variable                                               r.sub.3                                                                            41.23                                                                                   d.sub.3 6.00   N.sub.2                                                                            1.6779                                                                              ν.sub.2                                                                         53.4                            r.sub.4                                                                            181.25                                                                                  d.sub.4 1.89                                                   r.sub.5                                                                            30.51                                                                                   d.sub.5 4.08   N.sub.3                                                                            1.6545                                                                              ν.sub.3                                                                         33.9                            r.sub.6                                                                            23.05                                                                                   d.sub.6 12.79                                                  S    --                                                                                      d.sub. 7                                                                              Variable                                               r.sub.7                                                                            -23.05                                                                                  d.sub.8 4.08   N.sub.4                                                                            1.6545                                                                              ν.sub.4                                                                         33.9                            r.sub.8                                                                            -30.51                                                                                  d.sub.9 1.89                                                   r.sub.9                                                                            -181.25                                                                                 d.sub.10                                                                              6.00   N.sub.5                                                                            1.6779                                                                              ν.sub.5                                                                         53.4                            r.sub.10                                                                           -41.23                                                                                  d.sub.11                                                                              Variable                                               r.sub.11                                                                           -165.29                                                                                 d.sub.12                                                                              3.00   N.sub.6                                                                            1.6129                                                                              ν.sub.6                                                                         37.0                            r.sub.12                                                                           420.13                                                                   ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                        (Embodiment 6)                                                                ______________________________________                                        Magnification                                                                            -2.000       -1.000  -0.500                                        Focal length                                                                             168.10       190.47  168.10                                        Half view  16.6° 21.5°                                                                          16.6°                                  angle (ω)                                                               d.sub.2    6.696        0.570   6.696                                         d.sub.6    12.790       12.790  12.790                                        d.sub.7    6.668        12.790  6.663                                         .sub. d.sub.11                                                                           6.696        0.570   6.696                                         ______________________________________                                    

                  TABLE 13                                                        ______________________________________                                        (Embodiment 7)                                                                f = 230.208 to 203.134                                                                          F.sub.NO = 7.0                                              f.sub.1 /f.sub.M = -0.832                                                                       f.sub.2 /f.sub.M = 0.522                                    |r.sub.3 /r.sub.4 |, |r.sub.10 /r.sub.9            | = 0.479                                                                              r.sub.3 /r.sub.5 = r.sub.10 /r.sub.8 = 2.010                |n.sub.1 - n.sub.2 | = 0.078                                Radius of  Axial        Refractive Abbe                                       Curvature  Distance     Index      Number                                     ______________________________________                                        r.sub.1                                                                            -106.86                                                                                 d.sub.1 3.43   N.sub.1                                                                            1.6129                                                                              ν.sub.1                                                                         37.0                            r.sub.2                                                                            -1209.95                                                                                d.sub.2 Variable                                               r.sub.3                                                                            101.10                                                                                  d.sub.3 9.16   N.sub.2                                                                            1.6910                                                                              ν.sub.2                                                                         54.8                            r.sub.4                                                                            -211.17                                                                                 d.sub.4 8.07                                                   r.sub.5                                                                            50.30                                                                                   d.sub.5 9.59   N.sub.3                                                                            1.6545                                                                              ν.sub.3                                                                         33.9                            r.sub.6                                                                            37.72                                                                                   d.sub.6 12.67                                                  S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            -37.72                                                                                  d.sub.8 9.59   N.sub.4                                                                            1.6545                                                                              ν.sub.4                                                                         33.9                            r.sub.8                                                                            -50.30                                                                                  d.sub.9 8.07                                                   r.sub.9                                                                            211.17                                                                                  d.sub.10                                                                              9.16   N.sub.5                                                                            1.6910                                                                              ν.sub.5                                                                         54.8                            r.sub.10                                                                           -101.10                                                                                 d.sub.11                                                                              Variable                                               r.sub.11                                                                           1209.95                                                                                 d.sub.12                                                                              3.43   N.sub.6                                                                            1.6129                                                                              ν.sub.6                                                                         37.0                            r.sub.12                                                                           106.86                                                                   ______________________________________                                    

                  TABLE 14                                                        ______________________________________                                        (Embodiment 7)                                                                ______________________________________                                        Magnification                                                                            -2.000       -1.000  -0.500                                        Focal length                                                                             203.13       230.21  203.13                                        Half view  13.83°                                                                              18.05°                                                                         13.83°                                 angle (ω)                                                               d.sub.2    6.984        1.145   6.934                                         d.sub.6    12.669       12.669  12.669                                        d.sub.7    6.880        12.669  6.880                                         .sub. d.sub.11                                                                           6.934        1.145   6.934                                         ______________________________________                                    

                  TABLE 15                                                        ______________________________________                                        (Embodiment 8)                                                                f = 201.4 to 212.7   F.sub.NO = 8.0                                           f.sub.1 /f.sub.M = -1.158                                                                          f.sub.2 /f.sub.M = 0.637                                 (1/r.sub.2 = 1/r.sub.3)*f.sub.M = -1.878                                      |(r.sub.5 - r.sub.6 - d.sub.5)/f.sub.M | = 0.0145           Radius of  Axial        Refractive Abbe                                       Curvature  Distance     Index      Number                                     ______________________________________                                        r.sub.1                                                                            -129.68                                                                                 d.sub.1 3.00   N.sub.1                                                                            1.7006                                                                              ν.sub.1                                                                         30.1                            r.sub.2                                                                            -526.48                                                                                 d.sub.2 Variable                                               r.sub.3                                                                            144.26                                                                                  d.sub.3 20.00  N.sub.2                                                                            1.7130                                                                              ν.sub.2                                                                         53.9                            r.sub.4                                                                            -224.34                                                                                 d.sub.4 0.30                                                   r.sub.5                                                                            55.71                                                                                   d.sub.5 16.46  N.sub.3                                                                            1.5814                                                                              ν.sub.3                                                                         40.8                            r.sub.6                                                                            42.33                                                                                   d.sub.6 Variable                                               S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            -42.33                                                                                  d.sub.8 16.46  N.sub.4                                                                            1.5814                                                                              ν.sub.4                                                                         40.8                            r.sub.8                                                                            -55.71                                                                                  d.sub.9 0.30                                                   r.sub.9                                                                            224.34                                                                                  d.sub.10                                                                              20.00  N.sub.5                                                                            1.7130                                                                              ν.sub.5                                                                         53.9                            r.sub.10                                                                           -144.26                                                                                 d.sub.11                                                                              Variable                                               r.sub.11                                                                           526.48                                                                                  d.sub.12                                                                              3.00   N.sub.6                                                                            1.7006                                                                              ν.sub.6                                                                         30.1                            r.sub.12                                                                           129.68                                                                   ______________________________________                                    

                  TABLE 16                                                        ______________________________________                                        (Embodiment 8)                                                                ______________________________________                                        Magnification                                                                            -1.414       -1.000  -0.640                                        Focal length                                                                             205.8        212.7   201.4                                         Half view  23°   26°                                                                            22°                                    angle (ω)                                                               d.sub.2    3.348        1.166   4.789                                         d.sub.6    14.786       15.877  14.066                                        d.sub.7    14.786       15.877  14.066                                        .sub. d.sub.11                                                                           3.348        1.166   4.789                                         ______________________________________                                    

                  TABLE 17                                                        ______________________________________                                        (Embodiment 9)                                                                f = 201.4 to 212.6   F.sub.NO = 8.0                                           f.sub.1 /f.sub.M = -1.038                                                                          f.sub.2 /f.sub.M = 0.610                                 (1/r.sub.2 - 1/r.sub.3)*f.sub.M = -1.875                                      |(r.sub.5 - r.sub.6 -d.sub.5)/f.sub.M | = 0.0146            Radius of  Axial        Refractive Abbe                                       Curvature  Distance     Index      Number                                     ______________________________________                                        r.sub.1                                                                            -116.89                                                                                 d.sub.1 3.00   N.sub.1                                                                            1.6545                                                                              ν.sub.2                                                                         33.9                            r.sub.2                                                                            -618.28                                                                                 d.sub.2 Variable                                               r.sub.3                                                                            138.82                                                                                  d.sub.3 22.71  N.sub.2                                                                            1.6583                                                                              ν.sub.2                                                                         58.5                            r.sub.4                                                                            -178.19                                                                                 d.sub.4 1.74                                                   r.sub.5                                                                            50.61                                                                                   d.sub.5 14.20  N.sub.3                                                                            1.5814                                                                              ν.sub.3                                                                         40.8                            r.sub.6                                                                            39.51                                                                                   d.sub.6 Variable                                               S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            - 39.51                                                                                 d.sub.8 14.20  N.sub.4                                                                            1.5814                                                                              ν.sub.4                                                                         40.8                            r.sub.8                                                                            -50.61                                                                                  d.sub.9 1.74                                                   r.sub.9                                                                            178.19                                                                                  d.sub.10                                                                              22.71  N.sub.5                                                                            1.6583                                                                              ν.sub.5                                                                         58.5                            r.sub.10                                                                           -138.82                                                                                 d.sub.11                                                                              Variable                                               r.sub.11                                                                           618.28                                                                                  d.sub.12                                                                              3.00   N.sub.6                                                                            1.6545                                                                              ν.sub.6                                                                         33.9                            r.sub.12                                                                           116.89                                                                   ______________________________________                                    

                  TABLE 18                                                        ______________________________________                                        (Embodiment 9)                                                                ______________________________________                                        Magnification                                                                            -1.414       -1.000  -0.640                                        Focal length                                                                             205.7        212.6   201.4                                         Half view  23°   26°                                                                            22°                                    angle (ω)                                                               d.sub.2    3.542        1.658   4.789                                         d.sub.6    14.101       15.043  13.477                                        d.sub.7    14.101       15.043  13.477                                        .sub. d.sub.11                                                                           3.542        1.658   4.789                                         ______________________________________                                    

                  TABLE 19                                                        ______________________________________                                        (Embodiment 10)                                                               f = 201.4 to 212.4   F.sub.NO = 8.0                                           f.sub.1 /f.sub.M = -0.976                                                                          f.sub.2 /f.sub.M = 0.588                                 (1/r.sub.2 - 1/r.sub.3)*f.sub.m = -1.918                                      |(r.sub.5 - r.sub.6 - d.sub.5)/f.sub.M | = 0.0121           Radius of  Axial        Refractive Abbe                                       Curvature  Distance     Index      Number                                     ______________________________________                                        r.sub.1                                                                            -115.81                                                                                 d.sub.1  3.00  N.sub.1                                                                            1.6545                                                                              ν.sub.1                                                                         33.9                            r.sub.2                                                                            -799.72                                                                                 d.sub.2 Variable                                               r.sub.3                                                                            128.57                                                                                  d.sub.3 20.00  N.sub.2                                                                            1.6700                                                                              ν.sub.2                                                                         57.1                            r.sub.4                                                                            -184.46                                                                                 d.sub.4  0.30                                                  r.sub.5                                                                            49.32                                                                                   d.sub.5 13.62  N.sub.3                                                                            1.5814                                                                              ν.sub.3                                                                         40.8                            r.sub.6                                                                            38.28                                                                                   d.sub.6 Variable                                               S    --                                                                                      d.sub.7 Variable                                               r.sub.7                                                                            - 38.28                                                                                 d.sub.8 13.62  N.sub.4                                                                            1.5814                                                                              ν.sub.4                                                                         40.8                            r.sub.8                                                                            -49.32                                                                                  d.sub.9  0.30                                                  r.sub.9                                                                            184.46                                                                                  d.sub.10                                                                              20.00  N.sub.5                                                                            1.6700                                                                              ν.sub.5                                                                         57.1                            r.sub.10                                                                           -128.57                                                                                 d.sub.11                                                                              Variable                                               r.sub.11                                                                           799.72                                                                                  d.sub.12                                                                               3.00  N.sub.6                                                                            1.6545                                                                              ν.sub.6                                                                         33.9                            r.sub.12                                                                           115.81                                                                   ______________________________________                                    

                  TABLE 20                                                        ______________________________________                                        (Embodiment 10)                                                               ______________________________________                                        Magnification                                                                            -1.414       -1.000  -0.640                                        Focal length                                                                             205.7        212.4   201.4                                         Half view  23°   26°                                                                            22°                                    angle (ω)                                                               d.sub.2    3.657        1.947   4.789                                         d.sub.6    14.632       15.487  14.066                                        d.sub.7    14.632       15.487  14.066                                        .sub. d.sub.11                                                                           3.657        1.947   4.789                                         ______________________________________                                    

                  TABLE 21                                                        ______________________________________                                        (Embodiment 11)                                                               f = 201.7 to 213.0  F.sub.NO = 8.0                                            f.sub.1 /f.sub.M = -1.229                                                                         f.sub.2 /f.sub.M = 0.654                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -2.206                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0014             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -197.13    d.sub.1                                                                              3.00   N.sub.1                                                                            1.7006                                                                              υ.sub.1                                                                    30.1                            r.sub.2                                                                            2640.89    d.sub.2                                                                              Variable                                               r.sub.3                                                                            93.15      d.sub.3                                                                              13.00  N.sub.2                                                                            1.7130                                                                              υ.sub.2                                                                    53.9                            r.sub.4                                                                            -877.39    d.sub.4                                                                               0.30                                                  r.sub.5                                                                            48.26      d.sub.5                                                                              12.00  N.sub.3                                                                            1.5814                                                                              υ.sub.3                                                                    40.8                            r.sub.6                                                                            36.55      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -36.55     d.sub.8                                                                              12.00  N.sub.4                                                                            1.5814                                                                              υ.sub.4                                                                    40.8                            r.sub.8                                                                            -48.26     d.sub.9                                                                               0.30                                                  r.sub.9                                                                            877.39     d.sub.10                                                                             13.00  N.sub.5                                                                            1.7130                                                                              υ.sub.5                                                                    53.9                            r.sub.10                                                                           -93.15     d.sub.11                                                                             Variable                                               r.sub.11                                                                           -2640.89   d.sub.12                                                                              3.00  N.sub.6                                                                            1.7006                                                                              υ.sub.6                                                                    30.1                            r.sub.12                                                                           197.13                                                                   ______________________________________                                    

                  TABLE 22                                                        ______________________________________                                        (Embodiment 11)                                                               ______________________________________                                        Magnification                                                                             -1.414       -1.000  -0.640                                       Focal length                                                                              206.1        213.0   201.7                                        Half view   23°   26°                                                                            22°                                   angle (ω)                                                               d.sub.2     3.267        0.960   4.789                                        d.sub.6     15.799       16.952  15.038                                       d.sub.7     15.799       16.952  15.038                                       d.sub.11    3.267        0.960   4.789                                        ______________________________________                                    

                  TABLE 23                                                        ______________________________________                                        (Embodiment 12)                                                               f = 200.3 to 211.0  F.sub.NO = 8.0                                            f.sub.1 /f.sub.M = -0.729                                                                         f.sub.2 /f.sub.M = 0.489                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -1.955                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0113             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -95.35     d.sub.1                                                                              2.00   N.sub.1                                                                            1.5955                                                                              υ.sub.1                                                                    39.2                            r.sub.2                                                                            2354.33    d.sub.2                                                                              Variable                                               r.sub.3                                                                            103.20     d.sub.3                                                                              9.95   N.sub.2                                                                            1.6031                                                                              υ.sub.2                                                                    60.7                            r.sub.4                                                                            -135.13    d.sub.4                                                                              0.30                                                   r.sub.5                                                                            34.22      d.sub.5                                                                              7.98   N.sub.3                                                                            1.6545                                                                              υ.sub.3                                                                    33.9                            r.sub.6                                                                            28.62      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -28.62     d.sub.8                                                                              7.98   N.sub.4                                                                            1.6545                                                                              υ.sub.4                                                                    33.9                            r.sub.8                                                                            -34.22     d.sub.9                                                                              0.30                                                   r.sub.9                                                                            135.13     d.sub.10                                                                             9.95   N.sub.5                                                                            1.6031                                                                              υ.sub.5                                                                    60.7                            r.sub.10                                                                           -103.20    d.sub.11                                                                             Variable                                               r.sub.11                                                                           -2354.33   d.sub. 12                                                                            2.0    N.sub.6                                                                            1.5955                                                                              υ.sub.6                                                                    39.2                            r.sub.12                                                                           95.35                                                                    ______________________________________                                    

                  TABLE 24                                                        ______________________________________                                        (Embodiment 12)                                                               ______________________________________                                        Magnification                                                                             -1.414       -1.000  -0.640                                       Focal length                                                                              204.4        211.0   200.3                                        Half view   17°   20°                                                                            16°                                   angle (ω)                                                               d.sub.2     2.074        1.005   2.748                                        d.sub.6     14.097       15.116  13.423                                       d.sub.7     14.097       15.116  13.423                                       d.sub.11    2.074        1.005   2.748                                        ______________________________________                                    

                  TABLE 25                                                        ______________________________________                                        (Embodiment 13)                                                               f = 200.8 to 211.6  F.sub.NO = 8.0                                            f.sub.1 /f.sub.M = -0.757                                                                         f.sub.2 /f.sub.M = 0.495                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -2.182                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0028             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -123.98    d.sub.1                                                                              2.00   N.sub.1                                                                            1.6545                                                                              υ.sub.1                                                                    33.9                            r.sub.2                                                                            685.88     d.sub.2                                                                              Variable                                               r.sub.3                                                                            84.95      d.sub.3                                                                              9.95   N.sub.2                                                                            1.6935                                                                              υ.sub.2                                                                    50.3                            r.sub.4                                                                            -256.92    d.sub.4                                                                              0.30                                                   r.sub.5                                                                            37.67      d.sub.5                                                                              7.98   N.sub.3                                                                            1.6545                                                                              υ.sub.3                                                                    33.9                            r.sub.6                                                                            30.29      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -30.29     d.sub.8                                                                              7.98   N.sub.4                                                                            1.6545                                                                              υ.sub.4                                                                    33.9                            r.sub.8                                                                            -37.67     d.sub.9                                                                              0.30                                                   r.sub.9                                                                            256.92     d.sub.10                                                                             9.95   N.sub.5                                                                            1.6935                                                                              υ.sub.5                                                                    50.3                            r.sub.10                                                                           -84.95     d.sub.11                                                                             Variable                                               r.sub.11                                                                           -685.88    d.sub. 12                                                                            2.00   N.sub.6                                                                            1.6545                                                                              υ.sub.6                                                                    33.9                            r.sub.12                                                                           123.98                                                                   ______________________________________                                    

                  TABLE 26                                                        ______________________________________                                        (Embodiment 13)                                                               ______________________________________                                        Magnification                                                                             -1.414       -1.000  -0.640                                       Focal length                                                                              205.0        211.6   200.8                                        Half view   17°   20°                                                                            16°                                   angle (ω)                                                               d.sub.2     1.788        0.710   2.500                                        d.sub.6     13.967       15.045  13.255                                       d.sub.7     13.967       15.045  13.255                                       d.sub.11    1.788        0.710   2.500                                        ______________________________________                                    

                  TABLE 27                                                        ______________________________________                                        (Embodiment 14)                                                               f = 200.6 to 211.4  F.sub.NO = 8.0                                            f.sub.1 /f.sub.M = -0.818                                                                         f.sub.2 /f.sub.M = 0.517                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -2.390                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0026             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -157.52    d.sub.1                                                                              1.98   N.sub.1                                                                            1.6545                                                                              υ.sub.1                                                                    33.9                            r.sub.2                                                                            403.30     d.sub.2                                                                              Variable                                               r.sub.3                                                                            72.53      d.sub.3                                                                              6.90   N.sub.2                                                                            1.6935                                                                              υ2                                                                         50.3                            r.sub.4                                                                            -508.50    d.sub.4                                                                              0.28                                                   r.sub.5                                                                            38.55      d.sub.5                                                                              8.05   N.sub.3                                                                            1.6200                                                                              υ.sub.3                                                                    36.3                            r.sub.6                                                                            29.96      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -29.96     d.sub.8                                                                              8.05   N.sub.4                                                                            1.6200                                                                              υ.sub.4                                                                    36.3                            r.sub.8                                                                            -38.55     d.sub.9                                                                              0.28                                                   r.sub.9                                                                            508.50     d.sub.10                                                                             6.90   N.sub.5                                                                            1.6935                                                                              υ.sub.5                                                                    50.3                            r.sub.10                                                                           -72.53     d.sub.11                                                                             Variable                                               r.sub.11                                                                           -403.30    d.sub.12                                                                             1.98   N.sub.6                                                                            1.6545                                                                              υ.sub.6                                                                    33.9                            r.sub.12                                                                           157.52                                                                   ______________________________________                                    

                  TABLE 28                                                        ______________________________________                                        (Embodiment 14)                                                               ______________________________________                                        Magnification                                                                             -1.414       -1.000  -0.640                                       Focal length                                                                              204.8        211.4   200.6                                        Half view   17°   20°                                                                            16°                                   angle (ω)                                                               d.sub.2     1.403        0.221   2.183                                        d.sub.6     12.248       13.610  11.648                                       d.sub.7     12.428       13.610  11.648                                       d.sub.11    1.403        0.221   2.183                                        ______________________________________                                    

                  TABLE 29                                                        ______________________________________                                        (Embodiment 15)                                                               f = 201.0 to 212.1  F.sub.NO = 5.6                                            f.sub.1 /f.sub.M = -0.902                                                                         f.sub.2 /f.sub.M = 0.560                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -1.889                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0179             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -97.14     d.sub.1                                                                               4.00  N.sub.1                                                                            1.6477                                                                              υ.sub.1                                                                    33.9                            r.sub.2                                                                            -456.27    d.sub.2                                                                              Variable                                               r.sub.3                                                                            148.89     d.sub.3                                                                              10.00  N.sub.2                                                                            1.6516                                                                              υ.sub.2                                                                    58.6                            r.sub.4                                                                            -146.03    d.sub.4                                                                               0.30                                                  r.sub.5                                                                            44.34      d.sub.5                                                                              12.27  N.sub.3                                                                            1.5827                                                                              υ.sub.3                                                                    46.4                            r.sub.6                                                                            35.87      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -35.87     d.sub.8                                                                              12.27  N.sub.4                                                                            1.5827                                                                              υ.sub.4                                                                    46.4                            r.sub.8                                                                            -44.34     d.sub.9                                                                               0.30                                                  r.sub.9                                                                            146.03     d.sub.10                                                                             10.00  N.sub.5                                                                            1.6516                                                                              υ.sub.5                                                                    58.6                            r.sub.10                                                                           -148.89    d.sub.11                                                                             Variable                                               r.sub. 11                                                                          456.27     d.sub.12                                                                              4.00  N.sub.6                                                                            1.6477                                                                              υ.sub.6                                                                    33.9                            r.sub.12                                                                           97.14                                                                    ______________________________________                                    

                  TABLE 30                                                        ______________________________________                                        (Embodiment 15)                                                               ______________________________________                                        Magnification                                                                             -1.414       -1.000  -0.640                                       Focal length                                                                              205.3        212.1   201.0                                        Half view   17°   20°                                                                            16°                                   angle (ω)                                                               d.sub.2     2.068        0.653   3.000                                        d.sub.6     16.147       17.562  15.214                                       d.sub.7     16.147       17.562  15.214                                       d.sub.11    2.068        0.653   3.000                                        ______________________________________                                    

                  TABLE 31                                                        ______________________________________                                        (Embodiment 16)                                                               f = 200.9 to 212.0  F.sub.NO = 5.6                                            f.sub.1 /f.sub.M = -0.917                                                                         f.sub.2 /f.sub.M = 0.556                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -1.942                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0167             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -102.94    d.sub.1                                                                              2.00   N.sub.1                                                                            1.6545                                                                              υ.sub.1                                                                    33.9                            r.sub.2                                                                            -543.81    d.sub.2                                                                              Variable                                               r.sub.3                                                                            136.57     d.sub.3                                                                              8.23   N.sub.2                                                                            1.6700                                                                              υ.sub.2                                                                    57.1                            r.sub.4                                                                            -164.66    d.sub.4                                                                              0.30                                                   r.sub.5                                                                            44.20      d.sub.5                                                                              12.27  N.sub.3                                                                            1.5814                                                                              υ.sub.3                                                                    40.8                            r.sub.6                                                                            35.47      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -35.47     d.sub.8                                                                              12.27  N.sub.4                                                                            1.5814                                                                              υ.sub.4                                                                    40.8                            r.sub.8                                                                            -44.20     d.sub.9                                                                              0.30                                                   r.sub.9                                                                            164.66     d.sub.10                                                                             8.23   N.sub.5                                                                            1.6700                                                                              υ.sub.5                                                                    57.1                            r.sub.10                                                                           -136.57    d.sub.11                                                                             Variable                                               r.sub.11                                                                           543.81     d.sub.12                                                                             2.00   N.sub.6                                                                            1.6545                                                                              υ.sub.6                                                                    33.9                            r.sub.12                                                                           102.94                                                                   ______________________________________                                    

                  TABLE 32                                                        ______________________________________                                        (Embodiment 16)                                                               ______________________________________                                        Magnification                                                                             -1.414       -1.000  -0.640                                       Focal length                                                                              205.2        212.0   200.9                                        Half view   17°   20°                                                                            16°                                   angle (ω)                                                               d.sub.2     2.057        0.617   3.000                                        d.sub.6     16.160       17.597  15.214                                       d.sub.7     16.160       17.597  15.214                                       d.sub.11    2.057        0.617   3.000                                        ______________________________________                                    

                  TABLE 33                                                        ______________________________________                                        (Embodiment 17)                                                               f = 200.9 to 212.0  F.sub.NO = 5.6                                            f.sub.1 /f.sub.M = -0.914                                                                         f.sub.2 /f.sub.M = 0.555                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -1.870                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0172             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -108.03    d.sub.1                                                                              2.00   N.sub.1                                                                            1.7006                                                                              υ.sub.1                                                                    30.1                            r.sub.2                                                                            -532.90    d.sub.2                                                                              Variable                                               r.sub.3                                                                            143.96     d.sub.3                                                                              8.23   N.sub.2                                                                            1.7080                                                                              υ.sub.2                                                                    53.2                            r.sub.4                                                                            -176.01    d.sub.4                                                                              0.30                                                   r.sub.5                                                                            44.34      d.sub.5                                                                              12.27  N.sub.3                                                                            1.5814                                                                              υ.sub.3                                                                    40.8                            r.sub.6                                                                            35.73      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -35.73     d.sub.8                                                                              12.27  N.sub.4                                                                            1.5814                                                                              υ.sub.4                                                                    40.8                            r.sub.8                                                                            -44.34     d.sub.9                                                                              0.30                                                   r.sub.9                                                                            176.01     d.sub.10                                                                             8.23   N.sub.5                                                                            1.7080                                                                              υ.sub.5                                                                    53.2                            r.sub.10                                                                           -143.96    d.sub.11                                                                             Variable                                               r.sub.11                                                                           532.90     d.sub.12                                                                             2.00   N.sub.6                                                                            1.7006                                                                              υ.sub.6                                                                    30.1                            r.sub.12                                                                           108.03                                                                   ______________________________________                                    

                  TABLE 34                                                        ______________________________________                                        (Embodiment 17)                                                               ______________________________________                                        Magnification                                                                             -1.414       -1.000  -0.640                                       Focal length                                                                              205.2        212.0   200.9                                        Half view   17°   20°                                                                            16°                                   angle (ω)                                                               d.sub.2     2.058        0.628   3.000                                        d.sub.6     16.156       17.586  15.214                                       d.sub.7     16.165       17.586  15.214                                       d.sub.11    2.058        0.628   3.000                                        ______________________________________                                    

                  TABLE 35                                                        ______________________________________                                        (Embodiment 18)                                                               f = 200.9 to 212.0  F.sub.NO = 6.3                                            f.sub.1 /f.sub.M = -0.939                                                                         f.sub.2 /f.sub.M = 0.560                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -1.929                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0180             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -110.25    d.sub.1                                                                              2.00   N.sub.1                                                                            1.6545                                                                              υ.sub.1                                                                    33.9                            r.sub.2                                                                            -722.05    d.sub.2                                                                              Variable                                               r.sub.3                                                                            129.63     d.sub.3                                                                              8.23   N.sub.2                                                                            1.6700                                                                              υ.sub.2                                                                    57.1                            r.sub.4                                                                            -180.06    d.sub.4                                                                              0.30                                                   r.sub.5                                                                            42.48      d.sub.5                                                                              12.27  N.sub.3                                                                            1.5814                                                                              υ.sub.3                                                                    40.8                            r.sub.6                                                                            34.04      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -34.04     d.sub.8                                                                              12.27  N.sub.4                                                                            1.5814                                                                              υ.sub.4                                                                    40.8                            r.sub.8                                                                            -42.48     d.sub.9                                                                              0.30                                                   r.sub.9                                                                            180.06     d.sub.10                                                                             8.23   N.sub.5                                                                            1.6700                                                                              υ.sub.5                                                                    57.1                            r.sub.10                                                                           -129.63    d.sub.11                                                                             Variable                                               r.sub.11                                                                           722.05     d.sub.12                                                                             2.00   N.sub.6                                                                            1.6545                                                                              υ.sub.6                                                                    33.9                            r.sub.12                                                                           110.25                                                                   ______________________________________                                    

                  TABLE 36                                                        ______________________________________                                        (Embodiment 18)                                                               ______________________________________                                        Magnification                                                                             -1.414       -1.000  -0.640                                       Focal length                                                                              205.2        212.0   200.9                                        Half view   17°   20°                                                                            16°                                   angle (ω)                                                               d.sub.2     2.023        0.538   3.000                                        d.sub.6     16.191       17.676  15.214                                       d.sub.7     16.191       17.676  15.214                                       d.sub.11    2.023        0.538   3.000                                        ______________________________________                                    

                  TABLE 37                                                        ______________________________________                                        (Embodiment 19)                                                               f = 200.3 to 177.1  F.sub.NO = 8.0                                            f.sub.1 /f.sub.M = -0.694                                                                         f.sub.2 /f.sub.M = 0.490                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -1.907                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0057             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -81.54     d.sub.1                                                                              3.00   N.sub.1                                                                            1.5955                                                                              υ.sub.1                                                                    39.2                            r.sub.2                                                                            -5204.81   d.sub.2                                                                              Variable                                               r.sub.3                                                                            107.42     d.sub.3                                                                              9.00   N.sub.2                                                                            1.6031                                                                              υ.sub.2                                                                    60.7                            r.sub.4                                                                            -110.93    d.sub.4                                                                              0.30                                                   r.sub.5                                                                            36.80      d.sub.5                                                                              7.98   N.sub.3                                                                            1.6200                                                                              υ.sub.3                                                                    36.3                            r.sub.6                                                                            30.41      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -30.41     d.sub.8                                                                              7.98   N.sub.4                                                                            1.6200                                                                              υ.sub.4                                                                    36.3                            r.sub.8                                                                            -36.80     d.sub.9                                                                              0.30                                                   r.sub.9                                                                            110.93     d.sub.10                                                                             9.00   N.sub.5                                                                            1.6031                                                                              υ.sub.5                                                                    60.7                            r.sub.10                                                                           -107.42    d.sub.11                                                                             Variable                                               r.sub.11                                                                           5204.81    d.sub. 12                                                                            3.00   N.sub.6                                                                            1.5955                                                                              υ.sub.6                                                                    39.2                            r.sub.12                                                                           81.54                                                                    ______________________________________                                    

                  TABLE 38                                                        ______________________________________                                        (Embodiment 19)                                                               ______________________________________                                        Magnification                                                                             -2.000       -1.000  -0.500                                       Focal length                                                                              177.1        200.3   177.1                                        Half view   16°   21°                                                                            16°                                   angle (ω)                                                               d.sub.2     6.337        2.729   6.337                                        d.sub.6     8.615        12.223  8.615                                        d.sub.7     8.615        12.223  8.615                                        d.sub.11    6.337        2.729   6.337                                        ______________________________________                                    

                  TABLE 39                                                        ______________________________________                                        (Embodiment 20)                                                               f = 213.7 to 188.1  F.sub.NO = 8.0                                            f.sub.1 /f.sub.M = -0.932                                                                         f.sub.2 /f.sub.M = 0.571                                  (1/r.sub.2 -1/r.sub.3)*f.sub.M = -2.030                                       |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M | = 0.0074             ______________________________________                                        Radius of   Axial       Refractive Abbe                                       Curvature   Distance    Index      Number                                     ______________________________________                                        r.sub.1                                                                            -125.66    d.sub.1                                                                               3.00  N.sub.1                                                                            1.7006                                                                              υ.sub.1                                                                    30.1                            r.sub.2                                                                            -1273.06   d.sub.2                                                                              Variable                                               r.sub.3                                                                            114.67     d.sub.3                                                                              16.00  N.sub.2                                                                            1.7130                                                                              υ.sub.2                                                                    53.9                            r.sub.4                                                                            -234.56    d.sub.4                                                                               0.30                                                  r.sub.5                                                                            45.10      d.sub.5                                                                              10.00  N.sub.3                                                                            1.7170                                                                              υ.sub.3                                                                    47.9                            r.sub.6                                                                            36.24      d.sub.6                                                                              Variable                                               S    --         d.sub.7                                                                              Variable                                               r.sub.7                                                                            -36.24     d.sub.8                                                                              10.00  N.sub.4                                                                            1.7170                                                                              υ.sub.4                                                                    47.9                            r.sub.8                                                                            -45.10     d.sub.9                                                                               0.30                                                  r.sub.9                                                                            234.56     d.sub.10                                                                             16.00  N.sub.5                                                                            1.7130                                                                              υ.sub.5                                                                    53.9                            r.sub.10                                                                           -114.67    d.sub.11                                                                             Variable                                               r.sub.11                                                                           1273.06    d.sub.12                                                                              3.00  N.sub.6                                                                            1.7006                                                                              υ.sub.6                                                                    30.1                            r.sub.12                                                                           125.66                                                                   ______________________________________                                    

                  TABLE 40                                                        ______________________________________                                        (Embodiment 20)                                                               ______________________________________                                        Magnification                                                                             -2.000       -1.000  -0.500                                       Focal length                                                                              188.2        213.7   188.2                                        Half view   15°   19°                                                                            15°                                   angle (ω)                                                               d.sub.2     7.073        1.166   7.073                                        d.sub.6     9.973        15.880  9.973                                        d.sub.7     9.973        15.880  9.973                                        d.sub.11    7.073        1.166   7.073                                        ______________________________________                                    

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced other than as specifically described.

What is claimed is:
 1. A zoom lens system comprising from the objectside:a first lens unit of a negative power including a negative lenselement; a second lens unit of a positive power including a positivelens element and a negative meniscus lens element concave to the imageside; an aperture stop; a third lens unit arranged symmetrically withthe second lens unit with respect to the aperture stop; and a fourthlens unit arranged symmetrically with the first lens unit with respectto the aperture stop, wherein the second lens unit and the fourth lensunit are moved in a same direction in association with each other sothat the total length of the zoom lens system is minimum at unitymagnification, wherein the aperture stop moves so that the symmetry ofthe entire zoom lens system is maintained, and wherein an object-imagedistance is maintained constant by moving the entire zoom lens system.2. A zoom lens system as claimed in claim 1, wherein the second lensunit and the fourth lens unit are moved by a same amount.
 3. A zoom lenssystem as claimed in claim 1, wherein the distance between the firstlens unit and the second lens unit and the distance between the thirdlens unit and the fourth lens unit are minimum at unity magnification.4. A zoom lens system as claimed in claim 1, wherein said second lensunit consists of said positive lens element and said negative lenselement.
 5. A zoom lens system as claimed in claim 1, wherein the firstlens unit and the fourth lens units are bi-concave lens elements.
 6. Azoom lens system as claimed in claim 1, wherein the first lens unit andthe fourth lens units have the same absolute value for their radii ofcurvature symmetrical to the aperture stop.
 7. A zoom lens system asclaimed in claim 1, wherein the first and fourth lens units have thesame configuration and are arranged in a symmetrical manner, and thesecond and third lens units have the same configuration and are arrangedin a symmetrical manner.
 8. A zoom lens system comprising from theobject side:a first lens unit including a negative lens element concaveto the object side; a second lens unit including a positive lens elementand a negative meniscus lens element concave to the image side; anaperture stop; a third lens unit arranged symmetrically with the secondlens unit with respect to the aperture stop; and a fourth lens unitarranged symmetrically with the first lens unit with respect to theaperture stop; wherein the second lens unit and the fourth lens unit aremoved in a same direction in association with each other so that thetotal length of the zoom lens system is minimum at unity magnification,wherein an object-image distance is maintained constant by moving theentire zoom lens system, and wherein the following conditions arefulfilled:

    -1.3<f.sub.1 /f.sub.M <-0.7

    0.5<f.sub.2 /f.sub.M <0.7

    0<r.sub.3 /r.sub.4,r.sub.10 /r.sub.9 <0.3

    1.2<r.sub.3 /r.sub.5,r.sub.10 /r.sub.8 <1.8

where:f_(M) is a focal length of the zoom lens system at unitymagnification; f₁ is a focal length of the first lens unit; f₂ is afocal length of the second lens unit; r₃ is a radius of curvature of theobject side surface of the positive lens element of the second lensunit; r₄ is a radius of curvature of the image side surface of thepositive lens element of the second lens unit; r₅ is a radius ofcurvature of the object side surface of the negative meniscus lenselement of the second lens unit; r₈ is a radius of curvature of theimage side surface of a negative meniscus lens element of the third lensunit; r₉ is a radius of curvature of the object side surface of apositive lens element of the third lens unit; and r₁₀ is a radius ofcurvature of the image side surface of the positive lens element of thethird lens unit.
 9. A zoom lens system comprising form the object side:afirst lens unit including a negative lens element concave to the objectside; a second lens unit including a positive lens element and anegative meniscus lens element concave to the image side; an aperturestop; a third lens unit arranged symmetrically with the second lens unitwith respect to the aperture stop; a fourth lens unit arrangedsymmetrically with the first lens unit with respect to the aperturestop, wherein the second lens unit and the fourth lens unit are moved ina same direction in association with each other so that the total lengthof the zoom lens system is minimum at unity magnification, wherein anobject-image distance is maintained constant by moving the entire zoomlens system, and wherein the following conditions are fulfilled:

    -1.0<f.sub.1 /f.sub.M <-0.55

    0.4<f.sub.2 /f.sub.M <0.7

    0<r.sub.3 /r.sub.4,r.sub.10 /r.sub.9 <0.3

    1.2<r.sub.3 /r.sub.5,r.sub.10 /r.sub.8 <1.8

where:f_(M) is a focal length of the zoom lens system at unitymagnification; f₁ is a focal length of the first lens unit; f₂ is afocal length of the second lens unit; r₃ is a radius of curvature of theobject side surface of the positive lens element of the second lensunit; r₄ is a radius of curvature of the image side surface of thepositive lens element of the second lens unit; r₅ is a radius ofcurvature of the object side surface of the negative meniscus lenselement of the second lens unit; r₈ is a radius of curvature of theimage side surface of a negative meniscus lens element of the third lensunit; r₉ is a radius of curvature of the object side surface of apositive lens element of the third lens unit; and r₁₀ is a radius ofcurvature of the image side surface of the positive lens element of thethird lens unit.
 10. A zoom lens system comprising from the objectside:a first lens unit of a negative power including a negative lenselement; a second lens unit of a positive power including a positivelens element and a negative meniscus lens element concave to the imageside; an aperture stop; a third lens unit arranged symmetrically withthe second lens unit with respect to the aperture stop; and a fourthlens unit arranged symmetrically with the first lens unit with theaperture stop, wherein the second lens unit and the fourth lens unit aremoved in a same direction in association with each other so that thetotal length of the zoom lens system is minimum at unity magnification,wherein the zoom lens system is symmetrical with respect to the aperturestop at unity magnification whereas it is asymmetrical at amagnification other than unity magnification, wherein an object-imagedistance is maintained constant by moving the entire zoom lens system,and wherein the following conditions are fulfilled:

    -1.3<f.sub.1 /f.sub.M <-0.8

    0.5<f.sub.2 /f.sub.M <0.7

    |r.sub.3 /r.sub.4 |,|r.sub.10 /r.sub.9 |<0.5

    1.2<r.sub.3 /r.sub.5,r.sub.10 /r.sub.8 <2.2

    |n.sub.1 -n.sub.2 |<0.1

where:f_(M) is a focal length of the zoom lens system at unitymagnification; f₁ is a focal length of the first lens unit; f₂ is afocal length of the second lens unit; r₃ is a radius of curvature of theobject side surface of the positive lens element of the second lensunit; r₄ is a radius of curvature of the image side surface of thepositive lens element of the second lens unit; r₅ is a radius ofcurvature of the object side surface of the negative meniscus lenselement of the second lens unit; r₈ is a radius of curvature of theimage side surface of a negative meniscus lens element of the third lensunit; r₉ is a radius of curvature of the object side surface of apositive lens element of the third lens unit; r₁₀ is a radius ofcurvature of the image side surface of the positive lens element of thethird lens unit; n₁ is a refractive index of the negative lens elementof the first lens unit; and n₂ is a refractive index of the positivelens element of the second lens unit.
 11. A zoom lens system as claimedin claim 10, wherein the distance between the second lens unit and theaperture stop is different from the distance between the aperture stopand the third lens unit at a magnification other than unitymagnification.
 12. A zoom lens unit comprising from the object side:afirst lens unit including a negative lens element; a second lens unitincluding a biconvex lens element and a negative meniscus lens elementconcave to the image side; an aperture stop; a third lens unit arrangedsymmetrically with the second lens unit with respect to the aperturestop; and a fourth lens unit arranged symmetrically with the first lensunit with respect to the aperture stop, wherein the second lens unit andthe third lens unit are moved substantially symmetrically with respectto the aperture stop during zooming and wherein the following conditionsare fulfilled: -1. 3<f₁ /f_(M) <-0.6

    0.4<f.sub.2 /f.sub.M <0.7

    -3.0<(1/r.sub.2 -1/r.sub.3)f.sub.M <-1.5

    |(r.sub.5 -r.sub.6 -d.sub.5)/f.sub.M |<0.02

where:f_(M) is a focal length of the zoom lens system at unitymagnification; f₁ is a focal length of the first lens unit; f₂ is afocal length of the second lens unit; r₂ is a radius of curvature of theimage side surface of the negative lens element of the first lens unit;r₃ is a radius of curvature of the object side surface of the biconvexlens element of the second lens unit; r₅ is a radius of curvature of theobject side surface of the negative meniscus lens element of the secondlens unit; r₆ is a radius of curvature of the image side surface of thenegative meniscus lens element of the second lens unit; and d₅ is anaxial thickness of the negative meniscus lens element of the second lensunit.
 13. A zoom lens system as claimed in claim 12, wherein the firstlens unit and the fourth lens unit are arranged at predeterminedpositions with respect to the aperture stop, respectively.